This invention relates to a vehicle suspension system and particularly to a wheeled land vehicle suspension system.
In wheeled land vehicles it is common practice to provide a suspension system which serves to support the wheel and hub assemblies for movement relative to the chassis or body of the vehicle, with some form of springing being provided between each wheel and hub assembly and the chassis or body.
Under certain circumstances it can happen that a wheel and hub assembly reaches the limit of its possible movement towards the chassis or body, and in order to prevent the possibility of damage in such circumstances vehicles are generally provided with so-called `bump stop` in the form of a resilient member, often of rubber, against which part of the wheel and hub assembly strikes at the limit of its movement towards the chassis or body.
A disadvantage of such known bump stop arrangements is that striking of the wheel and hub assembly against the resilient member can occur with a high force resulting in jarring of the vehicle, and that after striking the resilient member the wheel and hub assembly rebounds, thus adversely affecting the ride quality and handling characteristics of the vehicle.
Recently vehicles have been developed having so-called active suspension systems (see for example EP-A-0114757 and U.S. Pat. No. 4,761,022) which utilize wheel and hub assembly suspension devices in the form of hydraulic actuators by which the wheel and hub assemblies are mounted to the chassis or body. These suspension devices are controlled by signals representing various movement parameters of the vehicle, such as heave, pitch, roll and warp modes of movement of the vehicle, and speed, and lateral and longitudinal acceleration of the vehicle, to obtain a desired ride quality and attitude for the vehicle under all driving conditions, the control signals being derived from appropriate transducers located at appropriate positions on the vehicle. In the system disclosed in U.S. Pat. No. 4,761,022 control signals are also obtained from steering angle and yaw rate sensors on the vehicle, the signals from these sensors being used to control the steering characteristics of the vehicle.